1. Field of the Invention
This invention relates in general to the analysis of particles using particle analyzers, and more particularly to using results obtained using a particle analyzer having a cell volume measurement device, a light scatter measurement device, or a cell conductivity measurement device, to further discriminate cell populations detected through a particle analyzer having a fluorescence measurement device.
2. Background
In medical diagnostic facilities, efficient and accurate diagnosis of blood and other bodily fluids is of key importance. Increased accuracy and efficiencies in terms of costs as well as time associated with the analysis of each sample are sought. Such medical diagnostic facilities employ at least two types of particle analyzers: hematology analyzers and flow cytometers. Hematology analyzers and flow cytometers measure and differentiate blood cells by collecting and analyzing signals produced when the blood cells pass through a small aperture or measurement region that is monitored by one or more sensors.
Hematology analyzers, in general, use electrical impedance to classify and count red and white blood cells based on their size and/or volume. Electrical impedance analysis involves transmitting an electrical current through a measurement region in the flow cell of the particle analyzer. The impedance of the current (measured between two terminals across the measurement region of the flow cell, for example) changes in relation to the cells that pass through. This is also known as the Coulter principle. Hematology analyzers can also utilize one or more beams of light to measure light scatter and reflectance to classify cells based on properties including size and granularity. Example hematology analyzers include COULTER® LH 700 Series manufactured by Beckman Coulter, and XE-2100™ manufactured by Sysmex.
Flow cytometers measure cell characteristics using detected fluorescence characteristics of cells when the cells are combined with one or more known fluorochromes. Labeling of the cells with fluorochromes that bind with high specificity to one particular cell type, makes it is possible to measure the contents of the cells. Such a fluorescent tag can be either a fluorescence dye molecule with a high binding-specificity for the particular component to be measured, or a fluorescence-conjugated antibody. The light scatter and reflectance of the cells yield information on their size, shape, and structure. Flow cytometers are capable of rapid, quantitative, multi-parameter analysis of heterogeneous cell populations on a cell-by-cell basis. Example flow cytometers include FC 500™ manufactured by Beckman Coulter, and FACSCanto™ manufactured by Becton Dickinson.
In laboratory settings, hematology analyzers and flow cytometers each have their respective strengths. Hematology analyzers are considered workhorse analytic instruments in that they are designed to economically process many routine assays per hour. For example, hematology analysis is widely used for such tests as complete blood count (CBC), reticulocyte analysis, and white blood cell differentials. Flow cytometers are used for additional tests that are generally costlier and more time consuming than those performed by hematology analyzers. Flow cytometry is particularly useful in the diagnosis and treatment of diseases such as leukemia, HIV/AIDS, and lymphomas, because it allows the monitoring of the proportion of a particular type of cell in the blood sample.
However, although hematology analyzers and flow cytometers are powerful analytical tools in and of their own accord, they each have limitations in the laboratory environment. Hematology analyzers cannot perform tests that detect proportion of cell types through the use of antibodies or fluorochromes. Flow cytometers are slow relative to hematology analyzers and require numerous costly antibodies and fluorochromes. Therefore, the need to harness the capabilities of both instruments to make a more robust particle analyzer system for medical diagnosis cannot be understated.
Presently, some blood samples are analyzed on a hematology analyzer as well as a flow cytometer. A typical scenario in a medical diagnostic facility can be the running of several hundred samples a day though a hematology analyzer, and then, for various reasons, having some of those samples further analyzed by a flow cytometer. For example, a flag generated by the hematology analyzer may represent the detection of a high white blood cell count. An example of a standing order to perform follow-on analysis in a flow cytometer may be for samples suspected of leukemia. Alternatively, and in some cases, samples flagged by the hematology analyzer can be further analyzed by a highly trained technician. The technician, typically, would prepare slides that are then manually examined. Also, in many cases, even having analyzed the sample through a flow cytometer, certain cell populations remain unresolved. In such cases, manual intervention is required by highly trained technicians to resolve the two separate sets of results generated by the hematology analyzer and the flow cytometer. Manual intervention by technologists is also costly, and introduces complications due to the potential for human error.
Some analytic instruments, such as the SAPPHIRE manufactured by Abbott Laboratories, combine aspects of a hematology analyzer with that of a flow cytometer. See, also, U.S. Pat. Nos. 5,939,326, 5,656,499, and 5,631,165. It is understood that the SAPPHIRE uses hematology analysis to determine characteristics such as total cell counts of cell types including cell types discovered in flow cytometry analysis. It is also understood that, at any given time, the SAPPHIRE can only operate either in the hematology analysis mode or in the flow cytometry mode. Having the instrument operate only in one mode at a time, for example, limits some of the advantages, such as speed and efficiency, of combining a hematology analyzer and flow cytometer.
Therefore, improved methods and systems for effectively leveraging capabilities of different types of particle analyzers are needed.